Undetected HIV infection and late diagnosis are major public health issues driven by inadequate uptake of HIV testing and counseling (HTC). HTC is the gateway to prevention and care services; however, roughly 60% of people living with HIV/AIDS in resource-poor countries are unaware of their status. In Zimbabwe, provider-delivered HTC (PDHTC) is widely available, yet late diagnosis (defined as receiving an AIDS diagnosis within a year of first positive test) remains common, suggesting that many high-risk individuals are not accessing timely HIV testing. In addition to limiting the clinical benefits of early care, persons with undetected infection may unknowingly transmit HIV to partners. Increasing the number of people who are aware of their serostatus is a priority as the first step on the continuum of HIV prevention and care services. HIV self-testing, where an individual collects their own sample and performs a simple rapid HIV test in the absence of a provider, has the potential to overcome a number of barriers hindering PDHTC approaches, and may therefore be effective at reaching individuals who are reluctant to test under current strategies. Simple-to-use oral HIV tests offer high sensitivity and specificity and do not pose a biohazard risk; consequently, they are ideal for self-testing. Though existing data indicate high demand and good accuracy of self-testing, we know little about how best to operationalize self-testing and facilitate linkage to HIV services. There is an urgent need for implementation research, particularly regarding preference for and uptake of self-testing, examining whether particular groups favor self-testing and exploring whether self- testing leads to timely engagement with HIV services and how best to facilitate this. We will address this gap by adapting a system to support self-testing and piloting this among adults in Zimbabwe to assess uptake and acceptability of self-testing compared with PDHTC. In Aim 1, we will adapt a culturally relevant set of self-testing materials that utilizes written and pictorial instructions, coupled with an innovative mobile phone system to support testing and engagement with HIV services, and evaluate these through supervised self-testing in a static HTC clinic. In Aim 2, we will use these materials to conduct an observational study in peri-urban communities, evaluating self-testing versus PDHTC to compare preference for testing methods and to assess key characteristics of testers and linkage to HIV services by testing method. Aim 3 will provide essential qualitative data exploring contextual aspects of self-testing, which will be critical to operationalizing this strategy, including how and where people self-test, why they opt to self- test, reasons why they did or did not link to HIV services, and potential safety concerns around self-testing. This project will generate materials and preliminary data to support scale-up of self-testing in Zimbabwe that could be applied to other countries. The findings will provide a critical foundation for future large-scale trials of the effectiveness of self-testing to increase uptake of HIV testin and engagement in HIV services.